The early version is without the input buffer. But maybe you could try to change some value or to add some parts.

This is the schematic of the version 1:

I never tried all these before, I just assume or read these tricks around:- If you need more bass you could try to increse C2- I'm not really sure, but if you increase C1 maybe you can cut some highs- Increase C3 to fatten your tone (the 2013 version use a 47uf)- To cut some highs the 2013 vesion use a 3.3nF cap before the Volume pot. But there is before, in series with the signal, a 10k resistor. You could try to include just the cap and see how it sounds, maybe you can use a smalle cap as 1nF.You can even try some different JFET, but you have to change the R4 resistor to get the right drain voltage, too. It should be close to 4.5v if you don't use a charge pump, I guess.

That is the schematic that I am using as a starting point. I built it as is and it sounds really good I just want to shave some of the brightness off and maybe make it just a touch fatter. Thanks for the suggestions I will try some out and see where it gets me.